Thursday, September 10, 2015

Hubble Uncovers Clues of Earliest Galaxies

The three panels show different components of near-infrared background
light detected by the Hubble Space Telescope in deep-sky surveys. The
one on the left is a mosaic of images taken over a 10-year period. When
all the stars and galaxies are masked, the background signals can be
isolated, as seen in the second and third panels. The middle panel
reveals "intra-halo light" from rogue stars torn from their host
galaxies, and the panel on the right captures the signature of the
first galaxies formed in the universe. Credit:NASA,ESA, and K. Mitchell-Wynne (University of California, Irvine). Released Images

Astronomers at the University of California at Irvine (UCI) and the
Space
Telescope Science Institute have made the most accurate statistical
estimate of the number of faint, small galaxies that existed only 500
million years after the big bang. This was culled from an analysis of
the
deepest Hubble Space Telescope sky survey, CANDELS (Cosmic
Assembly Near-Infrared Deep Extragalactic Legacy Survey). Previously,
studies using Caltech's CIBER (the Cosmic Infrared Background
Experiment) rocket-borne instrument and NASA's Spitzer Space
Telescope images confirmed the presence of "intra-halo light" from stars
distributed outside of galaxies. The Hubble data found a new component
in the infrared background in addition to intra-halo light — the
collective
glow of entire galaxies that formed first in the universe. UCI's Asantha
Cooray believes that these early galaxies are very different from the
well-defined spiral and disk-shaped galaxies seen in the present-day
universe.
They were more diffuse and populated by giant stars. This discovery
paves the way for NASA's James Webb Space Telescope to see these very
faint galaxies individually, after its launch in 2018.